Return line pipe size

Kasey Grohowski · Feb 19, 2019

Just wondering if the return line should be the same size pipe size as the drain pipes. I will be using 1 and 1/2 inch drain pipes, I will be drilling 2 3 inch holes in my tank for the overflow. Should I get a 1 and 1/2 inch bulkhead for my return line also? If so what size holesaw should I use?

FGourdin · Feb 19, 2019

Your return lines do not necessarily have to be as big as your inlet lines because the velocity of the flow is typically greater in the return lines. What will make the whole setup easier is to install ballvalves on all the lines to fine tune the flows. I have 2, 3" inlets to the sump and 2 , 1" returns and have to throttle back my inlets.

Kasey Grohowski · Feb 20, 2019

AllSignsPointToFish · Feb 20, 2019

I made both drain and return lines 1" PVC in my 125 gallon system. I don't really think that was necessary since my pump has sufficient head to overcome the minor losses in the 3/4" return lines. I was being overly cautious. The 1" return line didn't really help anything, but it didn't hurt anything, either.

Kasey Grohowski · Feb 20, 2019

AllSignsPointToFish said:
I made both drain and return lines 1" PVC in my 125 gallon system. I don't really think that was necessary since my pump has sufficient head to overcome the minor losses in the 3/4" return lines. I was being overly cautious. The 1" return line didn't really help anything, but it didn't hurt anything, either.

I think I will just make my return line of 1 inch, my return pump has up to 20 feet of head pressure so I should be more than good.

AllSignsPointToFish · Feb 20, 2019

Kasey Grohowski said:
I think I will just make my return line of 1 inch, my return pump has up to 20 feet of head pressure so I should be more than good.

That's what I did. I had to transition from 1" to 3/4" back to 1" through the pre-drilled bulkhead connection, but that is a minimal loss when compared to the entire line being 3/4" PVC.

ca1ore · Feb 20, 2019

Depends on the head pressure. I'd always go larger on the return. Even with a good pressure-rated pump, 1 1/2" pipe will significantly outperform 1". Like I said in your other thread (no need to have separate threads), always go pump native at least. My PW200 pushed about 1,000 gph through 1" PVC; 1,200 through 1 1/2". No brainer.

AllSignsPointToFish · Feb 20, 2019

ca1ore said:
Depends on the head pressure. I'd always go larger on the return. Even with a good pressure-rated pump, 1 1/2" pipe will significantly outperform 1". Like I said in your other thread (no need to have separate threads), always go pump native at least. My PW200 pushed about 1,000 gph through 1" PVC; 1,200 through 1 1/2". No brainer.

That's good advice, but you have to be careful not to run the pump off the end of the curve. Doing so can cause axial and radial vibration that will significantly reduce pump useful life.

Kasey Grohowski · Feb 20, 2019

AllSignsPointToFish said:
That's good advice, but you have to be careful not to run the pump off the end of the curve. Doing so can cause axial and radial vibration that will significantly reduce pump useful life.

What do you mean off of the end of the curve?

AllSignsPointToFish · Feb 20, 2019

Most pumps have a performance curve. Depending on the shape of the curve, you can get flowrates beyond the rated maximum if the downstream head and pressure requirements are reduced below those in the operating range. More flow occurs when you have fewer losses to overcome, but with that additional flow can come subsequent vibration. I don't know what kind of pump you're running, so I was just making you aware of that potential situation.

For illustration, you can see that curve E stops before 750gpm:

Kasey Grohowski · Feb 20, 2019

AllSignsPointToFish said:
Most pumps have a performance curve. Depending on the shape of the curve, you can get flowrates beyond the rated maximum if the downstream head and pressure requirements are reduced below those in the operating range. More flow occurs when you have fewer losses to overcome, but with that additional flow can come subsequent vibration. I don't know what kind of pump you're running, so I was just making you aware of that potential situation.

Jebao 13000 3645 gph 19.6 head pressure

AllSignsPointToFish · Feb 20, 2019

Kasey Grohowski said:
Jebao 13000 3645 gph 19.6 head pressure

You're probably okay in that case. The Jebao curves all intersect the x-axis, so you can't really run them off of the curve (assuming Jebao tested those pumps to that flowrate and didn't just extrapolate the curves).

Kasey Grohowski · Feb 20, 2019

AllSignsPointToFish said:
You're probably okay in that case. The Jebao curves all intersect the x-axis, so you can't really run them off of the curve (assuming Jebao tested those pumps to that flowrate and didn't just extrapolate the curves).

I'll pretend I know what you mean, lol.

AllSignsPointToFish · Feb 20, 2019

You can see in this graphic that all pump curves terminate on the flow axis (bottom). If you study the curves in the other diagram, you'll see that they end before touching the x-axis.